Do inline model forms emmit post_save signals? (django)

Question

So I have two models (Tables) related by a ForeignKey. In the admin, the edit page displays the first model (let's say ModelOne) along with the related instances of the second model, ModelTwo (TabularInline).

What I want is perform some additional actions when the second model is being changed. I can do this with a post_save signal on ModelTwo. However, the post_save signal is only called when I save the model from within its own edit page (ie. not within ModelOne's inlines).

Is there a way to attach a post_save signal on ModelTwo's inline form?

...As a workaround I added some custom validation to ModelTwo, which is being called regardless if it's inline or not), to call the method I want. However, the problem that arises from this setting is that if am creating a new instance of ModelOne and also create instances of ModelTwo at the same time I cannot access the primary key (foreign key) of the new instance that relates the two tables (since it has not been saved yet). And the primary key is something I need.

I also tried adding a post_save signal to ModelOne directly (so that I can get the new instance's PK) but it seems that the post_save signal does not pass ModelTwo's data (and why should it, anyway?)

So what's the solution to this? Do inline models emit signals? Is there a way to access the PK of the new instance before saving it?

Answer 1

Models are Models. The fact that a Model is used in the admin interface as inline doesn't take away from it in any way. All models emit a post save signal unless you override its functionality.

Here is what happens when you save any model.

Answer 2

Most of the time when a solution appeared to be solved with a signal, it ended up being solve better by overriding one of the various save methods. I have had a lot of success at injecting additional code at save time by overriding one of two methods:

1. The Admin Object's save_model method
2. The Model's save method.

Signals are still handy, but I've just had better luck at those two locations.

Answer 3

all the above are correct, just adding on more thing: when you save an object in admin (that contain inline), the 'post-save' signal of the inline (and of course the save method of the inline object) are triggered only if you made some changes to the inline object.